Federal safety inspectors are reviewing maintenance records and interviewing crew members to find out what caused a fatal explosion on a cruise ship in Miami this weekend.
The explosion in the Cruise Ship Norway's boiler room killed four crew members Sunday.
Two remain in critical condition.
National Transportation Safety Board investigators won't speculate the cause of the explosion.
But, they say a key factor is the age of the boiler, which investigators so far haven't been able to determine.
Coast Guard and police officials have said it appeared an accidental steam leak sparked the explosion.