MADISON, Wis. -- Madison police are investigating a pair of home invasions that occurred early Thursday morning.

Police said that both invasions have similar characteristics and said that they could be linked. Authorities said both invasions involved two men, one of whom was armed with a handgun.

Investigators said they believe both incidents were drug-related.

Police said that two men forced their way into a home on the 1900 block of Sachtjen Street on Madison's north side, near the Dane County Regional Airport, just before 3 a.m.

A couple was home in bed at the time and a woman was pistol-whipped by one of the assailants, who fled without taking anything. The woman is being treated for injuries.

About 40 minutes later, police said two men kicked in the door of an apartment in the in the 2100 block of Pike Drive on the city's south side.

Police said that the men confronted the sleeping couple, yelling "Where are the drugs?" and "Where is the money?" Police said one of the men punched the woman who lived in the Pike Drive apartment. Police said the men also rummaged through the couple's home but took nothing.

"We see, on occasion, where bad guys with guns get into apartments of people who are drug dealers and try to rip them off. That's not so unusual," said Joel DeSpain, public information specialist at the Madison Police Department. "What's unusual in these two cases is it looks like we've got people who got into homes of people who are not drug dealers -- just innocent people who were sleeping."

Authorities are asking anyone with information to call Crime Stoppers at 608-266-6014. Callers can remain anonymous.