The Israeli occupation was involved in the production of pagers that mass-detonated in the hands of thousands of people in Lebanon, an operation that took over 15 years of planning, ABC News reported on Friday citing a US intelligence source.

The unprecedented terrorist attack on Tuesday led to the killing of over 12 people and wounding more than 2,750. Casualties included women and children.

Read more: Snowden calls Israeli pager attack 'Indistinguishable from terrorism'

The firms suspected to have played the key role in the attack are Hungarian-based BAC Consulting, which Taiwan-based producer Gold Apollo says had permission to use its brand - including manufacturing - through a licensing agreement. Another company in Bulgaria is also suspected to have been part of the terrorist operation, yet it was unnamed by the country's authorities.

Sources said that the pagers were rigged with one to two ounces of explosives and equipped with a remote trigger to initiate the explosion.

Despite world countries and leaders expressing horror over the terrorist attack, the main concern among most Israeli officials and experts lies elsewhere.

A former senior Israeli intelligence officer criticized the timing of the detonation, considering it was a "wasted capability that was built to destroy Hezbollah."

Read more: New warfare era: Israelis weaponise consumer goods in terror attacks

"This is no less than a crime," he said, likening it to "shooting an Arrow or David's sling missile at the Independence Day fireworks show."

"This thing should have been saved for the right time," he maintained.

The ABC News source said the planning for the attack utilized shell companies, with multiple tiers of Israeli intelligence agents and their operatives operating under the guise of a legitimate business producing the pagers. The source also claimed that some operatives participating in the work were unaware of who they were working for.

Hezbollah Secretary-General Sayyed Hassan Nasrallah said in a Thursday speech that the Israeli goal was to massacre thousands of people simultaneously in the Tuesday and Wednesday terrorist attacks, referring as well to the detonation of rigged two-way radios on Wednesday.

"Not all of the pagers had been distributed and some of them were turned off," Sayyed Hassan Nasrallah said, adding that the Resistance party has launched a comprehensive investigation into the attack

"Over two days [Tuesday and Wednesday], the enemy wanted to kill at least 5,000 people ... The enemy knew that the pager devices numbered 4,000."

Taiwan, Bulgary, and Hungary trying to absolve themselves

Taipei is 'certain' yet still investigating

Two individuals from Taiwanese companies linked to the manufacturing of the booby-trapped electronic devices have been questioned by the island's authorities.

According to Reuters, one of the people questioned was Taipei-based Gold Apollo's president and founder, Hsu Ching-kuang. He was questioned by prosecutors late into the night on Thursday, before being released. The other person was Teresa Wu, the sole employee of a company called Apollo System.

Meanwhile, Taiwan's Economy Minister Kuo Jyh-huei said, "Components used in thousands of pagers that detonated on Tuesday in Lebanon were not made in Taiwan. The components are (mainly) low-end IC (integrated circuits) and batteries."

Read more: UN Security Council to address Israeli pager attacks on Lebanon Friday

"I can say with certainty they were not made in Taiwan," Kuo claimed, adding the case is being investigated by judicial authorities.

Taiwan's Foreign Minister Lin Chia-lung, when asked by reporters if he had contacted the de facto Israeli ambassador to the island to express concern about the issue, responded, "No".

"We are asking our missions abroad to raise their security awareness and will exchange relevant information with other countries," Lin said.

However, a spokesperson for the Shilin District Prosecutors Office said they are still looking into whether any Taiwan-based firm was involved in the terrorist attack.

The spokesperson told Reuters, "We'll seek to determine if there was any possible involvement of these Taiwanese companies as soon as possible, to ensure the safety of the country and its people."

'Indisputable' 24-hour investigation

Less than 24 hours after announcing the launch of an investigation on Thursday, the Bulgarian State Agency for National Security concluded that it "indisputably established" that the pagers used in the terrorist explosions in Lebanon were not imported to, exported from, or produced in Bulgaria.

A spokesperson for the Hungarian government claimed on Wednesday that the pagers were "never" in Hungary, telling the news outlet that the company involved in the terrorist attack was "a trading intermediary, with no manufacturing or operational site in Hungary."

Read more: Exclusive: Hezbollah strike against Glilot base highly successful

“Authorities have confirmed that the company in question is a trading intermediary, with no manufacturing or operational site in Hungary,” government spokesperson Zoltan Kovacs said in a post on X.

Hungarian news site Telex reported earlier this week that the shipment of the Israeli-rigged pagers that was handled by the Bulgarian company Norta Global Ltd., while the Hungarian company BAC Consulting Kft. served merely as an intermediary.

Bulgaria being set-up by Hungary?

Similarly, Bulgaria also claimed that the country had nothing to do with the attack,

Bulgarian State Agency for National Security said on Friday that the pagers used in the terrorist explosions in Lebanon were not imported to, exported from, or produced in the country.

On Thursday, Bulgarian authorities stated that the Interior Ministry and state security services had initiated an investigation into a company's possible connection to the sale of pagers, without naming the company.

Vasil Stefanov MP of Continue the Change - Democratic Bulgaria responded to the Telex report, saying, "Hungary is looking for a scapegoat to shift the focus of attention away from itself because the probe has reached Hungarian trade intermediaries."

"It is very important to use solely and exclusively the official sources of information and not to speculate at such moments," Stefanov said.