CHICAGO (CBS) — Police in Round Lake Park announced Monday they were working with the feds to try to find missing mom Melissa Ann Best, then later said an announcement in the case was expected Tuesday.

Round Lake Park police Chief George Filenko says the FBI has now assigned a field agent to the case, which has been classified as a missing person’s investigation.

Best was last seen April 15 when she dropped her daughter off at a friend’s house. Surveillance from a nearby restaurant shows her driving her van, but that van has not been found.

LISTEN: Newsradio 780’s Mary Frances Bragiel Reports

Filenko tells Newsradio 780’s Mary Frances Bragiel that because Best did not have a cell phone or own credit cards, he has instructed law enforcement agencies to begin looking in parking lots and motels. Authorities are also using a tracking device that locates license plates.

While police have been called to the Bests’ house in the past for verbal disturbances, Best’s husband, Clinton, has been very cooperative, according to Falenko and has been talking to police daily.

Police said a news conference would be held at 11 a.m. Tuesday but would not give any information.

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