(Reuters) - Twelve people were missing on Thursday, a day after a blast at the site of an optical electronics factory 50 km (30 miles) northeast of Moscow killed one person and injured more than 60.
Investigators say pyrotechnic equipment was being stored in the rented warehouse on the grounds of the Zagorsk Optical and Mechanical Plant where the blast occurred. At least 30 people were admitted to hospital, including six to intensive care.
The factory produces optical equipment for industrial and healthcare applications as well as for the Russian security forces.
Olga Vradiy, of the Moscow region branch of the federal Investigative Committee, said the technical director of Pyro-Ross, a now-bankrupt pyrotechnics firm, had been detained on suspicion of violating safety regulations, the Interfax news agency reported.
Vradiy also said the number of those listed as missing had risen to 12.
Around 38 apartment blocks in the surrounding area were damaged by the explosion, mostly with broken windows, along with two schools, a sports complex and a store, the governor of the Moscow region said on Wednesday.
The TASS news agency quoted emergency services as dismissing early reports that the blast could have been caused by a drone attack, many of which have taken place in Moscow and the surrounding area in recent weeks and months, attributed by Russia to Ukraine.
(Reporting by Reuters; writing by Kevin Liffey; editing by Philippa Fletcher)