TOKYO — The Japanese manufacturer of the two-way radios reportedly detonated in a second round of explosions targeting the militant group Hezbollah in Lebanon said Thursday that it was investigating the allegations, but early signs pointed to the walkie-talkies being counterfeit.

       The explosions linked to the electronic devices killed at least 20 people and injured more than 450 across Lebanon on Wednesday, a day after 12 people were killed and thousands wounded by exploding pagers in a suspected Israeli attack.

       The source of Wednesday’s explosions was not immediately clear. Lebanon’s state news agency said some of the explosions occurred in a brand of two-way radio, with images from the scenes of the explosions showing walkie-talkies bearing the brand name Icom and the model number V82.

       Icom, a Japanese manufacturer of radio equipment, said in a statement on its website Thursday morning that it produced the IC-V82 handheld radio from 2004 to October 2014 and shipped it to overseas markets, including in the Middle East, during that period. But there had been no shipments since the model was discontinued about 10 years ago, and the production of batteries to operate the unit had also been discontinued, the company said.

       Furthermore, the photos of the devices did not show the hologram sticker that Icom had attached to the units to prevent counterfeiting, “so we cannot confirm whether the product was shipped from our company or not,” the statement said.

       Osaka-based Icom, founded in 1954, is a manufacturer of wireless communication products. The company produces communication receivers including amateur, marine and aviation radios, and navigation products. They are sold in more than 80 countries around the world, with subsidiaries in the United States, Australia, Germany, Spain and China, according to Icom’s website.

       The company said its products were sold overseas only to its authorized distributors and that it had strict export controls in place, in line with Japanese government regulations.

       The Japanese government was also closely monitoring the reports. “We are currently gathering information,” Yoshimasa Hayashi, chief cabinet secretary, told reporters in Tokyo on Thursday morning.

       Yoshiki Enomoto, the general manager of Icom’s security and trade division, told the Kyodo News agency that the device could be its IC-V82 model, although the company couldn’t yet rule out “the possibility of a fake.”

       “The battery may have been replaced with a battery that was modified to explode after the product was acquired,” Kyodo quoted Enomoto as saying.

       Earlier, a sales executive at Icom’s U.S. subsidiary told the Associated Press that the exploded devices appeared to be a knockoff product that was not made by Icom.

       “I can guarantee you they were not our products,” the AP quoted Ray Novak, a senior sales manager for Icom America’s amateur radio division, as saying during an interview Wednesday at a trade show in Providence, R.I.

       Novak said Icom introduced the V82 two-way radio model over two decades ago and that it had long since been discontinued. He said people used the device in emergency communications, including to track tornadoes or hurricanes, and that amateur radio operators also used it.

       Hezbollah had moved to older technologies for communication, deeming cellphones too easy to compromise. But this week’s attacks, which have been attributed to Israel’s military, have challenged that thinking.

       Israel, which rarely comments on its intelligence operations abroad, has neither claimed nor denied responsibility for the attacks.

       The explosions Tuesday, which killed at least 12 people and injured as many as 2,800, were caused when the pagers were simultaneously detonated. Experts said they were probably intercepted before delivery and rigged with explosives.

       The pagers bore the logo of Taiwanese manufacturer Gold Apollo, which has denied making the devices and said they were “entirely handled” by a Hungarian company called BAC Consulting KFT, which was authorized to use Gold Apollo’s brand trademark in some regions.

       Taiwanese Defense Minister Wellington Koo said the Taipei government was closely watching developments. “The relevant national security bodies are paying great attention to this,” he said in remarks released Thursday.

       The Washington Post could not reach BAC for comment and the government of Hungary denied links to the devices. Hungarian government spokesman Zoltan Kovacs said on social media that BAC is a “trading intermediary, with no manufacturing or operational site in Hungary. It has one manager registered at its declared address, and the referenced devices have never been in Hungary.”

       Pei-lin Wu in Taipei contributed to this report.