CONCORD, Calif. (AP) - Officials want Whitney Houston to reimburse the city for the $100,000 spent preparing for a concert she canceled 15 minutes before show time.

Houston said she bowed out of an Aug. 1 concert at the public-owned Concord Pavilion because she was ill. About 5,000 fans were in their seats when the announcement was made, and thousands more were turned around in the parking lot.

City officials said about 8,500 tickets of a possible 12,500 had been sold.

The Pavilion's booking agent, San Francisco-based Bill Graham Presents, said Houston's representatives had promised to look into the matter.

Questions faxed Wednesday to agent Nancy Seltzer were not answered.

The singer had canceled four earlier dates on her summer tour, citing throat problems and a "bronchitis situation".