Sept. 9 (UPI) -- Russian cosmonauts woke up to an emergency alarm Thursday in one of their service modules at the International Space Station.
Audio from NASA's television feed caught a French astronaut identifying a smell of burning plastic, according to Radio Free Europe/Radio Liberty.
Russian space agency Roscosmos told state news agency TASS that the cosmonauts turned on an air purification system. The action appeared to eliminate the smell. It was not known Friday what caused the smell.
"After the air purification, the crew members continued their rest," the Russian space agency said.
Roscosmos said preparation for a spacewalk the cosmonauts were planning to take later Thursday continued after the incident.
"According to the data of the main operational control group of the Russian segment at the station, all systems are operating normally, the composition of the air on board the station is in line with the standard indicators," Roscosmos said. "The crew continued regular preparation for today's spacewalk."
The cosmonauts, Oleg Novitsky and Pyotr Dubrov, connected various cables and mount rails on the external surface of the Nauka module.