The disappearance of a Russian oil tanker in Nigerian custody is a "national embarrassment" says a senior MP investigating the case.
A second oil tanker may also have disappeared in Nigeria.
Nigeria's navy seized MT African Pride tanker along with 13 Russian sailors, on suspicion of smuggling last October.
But the tanker, laden with crude oil, disappeared last month. Navy and police officials have blamed each other.
Some 30,000 barrels of oil are lost to fuel thieves each day in Nigeria, officials say.
The mysterious disappearance is "an episode that belonged to the old Nigeria," Anthony Aziegbemi , chairman of the parliamentary committee conducting the investigation, said in a statement.
He said the navy committee is resolved to get to the bottom of the disappearing act.
"The rule of law should catch up with anybody no matter how highly placed," he said.
The defence minister and other naval officers have been asked to appear before the committee this week.
Another ship detained in connection with the alleged theft of oil, the MT Jimoh, might also have gone missing with its cargo of crude oil last week, although this was not confirmed, Mr Aziegbemi said.
Nigeria is Africa's largest oil exporter.