WASHINGTON (Reuters) - Capitol Police are investigating a series of small fires that have occurred over the past month in Senate office buildings, mostly in women's restrooms, a spokeswoman said on Friday.

A small fire early on Friday in a second-floor restroom of the Dirksen Senate office building brought to at least seven the number of confirmed fires since the beginning of October, according to Sgt. Kimberly Schneider, a Capitol Police spokeswoman.

She would not discuss the possible cause of the fires, which she said were still under investigation.

Fires have been discovered in all three buildings that house senators' offices and hearing rooms, Schneider said. The buildings are adjacent to the U.S. Capitol.

She added that all the fires have been extinguished quickly and there have been no injuries.