JOLIET, Ill. (WBBM) — Police say money and drugs may be at the center of a series of nighttime home invasions where residents were tied up with duct tape.

There have been four invasions for far, two in Joliet and two in Crest Hill, reports Newsradio 780’s Steve Miller.

Joliet Police Cmdr. Benjamin Billups says the same men were probably involved in all four.

LISTEN: Newsradio 780’s Steve Miller Reports

The common thread?

“Were not quite certain at this point if all of these incidents are drug related. … But there are some ties there,” Billups said.

“It seems like they know who their victims are and are targeting specific people.”

Cmdr. Billups said money was taken in all four crimes. Police have some leads in the case and are continuing to investigate persons of interest.