By Chris Borowski

WARSAW (Reuters) - Relatives of the victims of a plane crash that killed Poland's president and 95 others in 2010 are facing the possibility that they buried strangers instead of their loved ones due to mistakes identifying remains.

Polish prosecutors said on Tuesday that the remains of Anna Walentynowicz, one of the people killed in the crash near the Russian city of Smolensk, were mixed up with those of another victim.

That revelation has raised questions about how many of the other bodies were wrongly identified after the crash - an event which traumatized the nation and still complicates relations with Poland's neighbor Russia.

Prosecutors have so far ordered that the remains of four victims should be exhumed to check if they are indeed the people their relatives thought they buried.

"I don't want to say that there will be a wave of exhumations just yet, but it won't end with just four," said Rafal Rogalski, a lawyer representing the relatives of several victims, including former President Lech Kaczynski.

"What has happened only underlines the approach of the Russian authorities and how reliable their documentation is. For now I can say that I am only certain (about the identity) of 10 or 11 bodies," he told Reuters.

Lawyers and relatives said on Wednesday they were considering requesting that many more bodies be unearthed.

The crash has particular poignancy for Poles because it evokes memories of the Katyn massacre, when Soviet secret police murdered an estimated 22,000 Poles in a forest during World War Two. The crash victims were travelling to Smolensk to take part in ceremonies to mark Katyn's fiftieth anniversary.

"ETERNAL INFAMY"

The remains of the Smolensk victims were examined by Russian investigators in the presence of Polish officials in Moscow before being flown back to Warsaw in metal coffins. They were then handed over to relatives for burial.

Opposition leader Jaroslaw Kaczynski, twin brother of the late president who died in the crash with other civilian and military officials, accused the government of Polish Prime Minister Donald Tusk of failing to make sure Russian officials dealt properly with the remains.

"The people responsible for what happened with the exhumation should leave Polish politics and leave in eternal infamy," said Kaczynski, who has been accused of seeking to score political points from the disaster.

The Justice Minister was scheduled to discuss the exhumations at a parliamentary session on Thursday.

"The original sin was when Poland decided not to work with Russian investigators hand-in-hand immediately after the crash," said Stefan Hambura, an attorney for the family of Walentynowicz. A former Solidarity activist, her case sparked the review of how the remains were identified.

Russian investigators have blamed the crew of the Polish government Tu-154 for the crash, while a Polish report pointed the finger at Russian ground controllers for allowing the jet to land in heavy fog at a small airport near Smolensk.

Hambura told Reuters he had already asked military prosecutors to test the remains of Stefan Malak, a Smolensk victim, at the request of his brother.

Magdalena Merta, a widow of another victim, said she regretted not checking whether it really was the body of her husband that had lain in the coffin she kept in her home before the funeral.

"This was a chance to establish his identity," she told Polish television.

"I regret that I did not stand up to my family in this matter, but they feared that opening it would have been the last thing I did in my life."

(Additional reporting by Pawel Sobczak; Editing by Andrew Osborn)