In the case of Monday’s fire, firefighters may not have known the home they were about to enter, vacant since at least 2010, had caught fire six years ago, injuring three firefighters. The city condemned it as a result of that fire, and offered it for sale due to unpaid taxes, but it found no takers, so it remained with its owners, said Tammy Hawley, spokeswoman for the city housing department. Efforts by The Baltimore Sun to reach them were unsuccessful.