Source: Aspen Social Services Contacts L.A. County About Charlie Sheen's Twins

Pitkin County looking to establish whether they or L.A. County Department of Children and Family Services has jurisdiction, if they're needed

One arrest can lead to a lot of phone calls.

Aspen's Pitkin County Department of Social Services contacted the Los Angeles Department of Children and Family Services as part of a routine investigation into the welfare of Charlie Sheen's 9-month-old twin sons, Bob and Max, a source tells E! News.

Such a follow-up is standard procedure in cases that involve a charge of domestic violence. Sheen was arrested on suspicion of felony menacing and assault on Christmas Day for allegedly threatening wife Brooke Mueller with a knife. He's due in court Feb. 8.

Pitkin County officials learned that there are no outstanding investigations concerning Sheen's kids in L.A., the source says.

So what else did they want to know then?

Our source tells us that investigators are looking into who would have jurisdiction over the fate of the children—Aspen or L.A.

What is at issue here, the insider says, is whether the twins have at any point "continuously resided" in Colorado for 90 days. If so, the Rocky Mountain state may have authority to determine whether the children are safe in the custody of either parent.

Reports that both agencies were looking into the case arose yesterday, but L.A.'s DCFS would not confirm any involvement.

"We are not allowed to disclose, be it a celebrity or anyone, whether they are even in our system or whether we are doing an investigation," spokesman Neil Zanville told E! News Wednesday.

A rep for Sheen was not able to be reached for comment.

As of yesterday, Max and Bob were in Aspen with Mueller and at least one nanny, while Sheen's rep has confirmed that the actor returned to L.A.

—Additional reporting by Ashley Fultz

(Originally published Dec. 30, 2009, at 9 p.m. PT)