(Reuters) - Law enforcement officials in a small southern Indiana city were the target of two explosive devices that were detonated over the past nine days, police said on Thursday.

A homemade device exploded in the driveway of a judge on Wednesday in Madison, Indiana. Authorities in the town were already investigating a similar device that detonated in the police department’s parking lot on March 6, Madison Police Chief Dan Thurston told a news conference.

“We are considering these explosions as a message and a direct threat to members of the criminal justice system in our local community,” Thurston said.

No injuries were reported in either explosion. Thurston said Madison law enforcement officials, their families and their neighbors should be vigilant in the city of about 12,000 people about 100 miles (160 km) south of Indianapolis.

Thurston said there were consistencies between the two explosions that were leading investigators to believe that the same person or persons were responsible for both.

Witnesses heard the explosions, which occurred at night, but did not immediately notify police, according to Thurston.

The U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives is analyzing both devices to determine how they were made and the size of the explosions, Thurston said.

(This story has been refiled to correct date in dateline)