Moscow ? Residue of the same type of explosive found in the wreckage of one of two Russian airliners that crashed last week has been found in the second, authorities said Saturday.

“Traces of hexogen were found in the course of an additional investigation of fragments of the Tu-134 airplane that crashed in the Tula region,” Sergei Ignatchenko, a spokesman for the Federal Security Service, or FSB, told the Russian news agency Interfax.

The FSB had announced Friday the discovery of traces of hexogen in the wreckage of the other plane, which crashed in Russia’s southern Rostov region. Ninety people died in the crashes after both jets took off from the same Moscow airport Tuesday night.

Investigators’ suspicions appeared to be focused on two women with Chechen-sounding surnames, one believed to have been on each flight, as possible suicide bombers. Authorities have said that no one has come forward to claim either body and that both women booked seats shortly before departure.

The bodies of 43 out of 44 people killed in the Tu-134 crash have been positively identified, and body parts of the last person, a woman, have been sent to Moscow for identification and examination to find out whether there are traces of explosives, the news agency Itar-Tass reported. That woman is believed to be Amanta Nagayeva, who was on the passenger list for the flight from Moscow to the southern city of Volgograd, which crashed about 100 miles south of Moscow.

In a further indication that at least one of the women might have been a suicide bomber, the newspaper Izvestia reported Saturday that Nagayeva’s brother had been seized by Russian forces in separatist Chechnya about three years ago.

Human rights organizations say that Russian troops in Chechnya have a history of abducting suspected rebels or rebel supporters and executing them.