SEATTLE -- The Seattle Fire Department is investigating whether a string of weekend trash bin fires in the lower Queen Anne neighborhood is the work of an arsonist.

Melted plastic containers with burned recyclables inside marked the scene of a fire behind the Viking Apartments on Second Avenue West.

Residents there said the weekend fire was the second one in a month.

"It is scary," said Andrew Stark. "It happens in the middle of the night, and you are concerned for your life, really."

Seattle fire investigators told KIRO 7 Eyewitness News that the most recent fire behind the Viking is a case of arson, but they believe a fire there a month ago was accidental.

Resident Sara Dore said she feels uneasy about what's happened outside her apartment.

"I've lived here for four years, and this hasn't been a problem until recently," Dore said.

While reporter Chris Egert was looking around the neighborhood near Dore's apartment, he found another burned trash bin behind an apartment building across Second Avenue.

Firefighters weren't aware of that fire, and -- after Egert told firefighters about it -- investigators will look to see if the cases may be connected.

Arson investigators said they don't have a suspect, a motive, or a witness.