MOSCOW (AP) _ Cosmonaut Yuri Romanenko, who has been in space almost 11 months, and a companion have begun packing their Soyuz spacecraft for their return to Earth on Tuesday, the Tass news agency said.

Tass said Romanenko, who holds the space endurance record, and flight engineer Alexander Alexandrov are putting ''documents, photo and cinema film to be developed, magnetic tape, packed biological objects'' into the Soyuz TM- 3 craft.

They will return Tuesday from the Mir orbiting space complex along with test pilot Anatoly Levchenko, who accompanied two other cosmonauts to the station Wednesday.

Soviet media has reported that the other two cosmonauts, Vladimir Titov and Musa Manarov, are to remain aboard the space station for about a year, thereby breaking Romanenko's record.

Romanenko has been in space since Feb. 6. He rocketed to the Mir space station with Alexander Laveikin, but Laveikin was replaced in July by Alexandrov.

Tass said the five cosmonauts were conducting final experiments on growing crystals of vegetable protein.

''Documents of the research conducted during a long flight and of the experiments staged by the two crews during the change of shifts on board the orbital complex will be brought to the Earth,'' Tass said.

Soviet space officials have said they are very interested in Romanenko's physical condition after 11 months in space because it will help determine how long man can live unimpared in weightlessness.

They say that will help determine the possibility of a trip to Mars, which would take about three years.

Other space missions are planned for the Mir complex while Titov and Manarov are aboard, including a joint Soviet-Bulgarian mission.