At least 250 people are stranded at Westfield Woden Shopping Centre, unable to access their cars while police investigate a suspicious package left in the underground carpark.

ACT Policing responded to a call by centre management reporting the package at about 4.30 this afternoon, and subsequently closed the carpark.

Westfield Woden PR manager Julia Clarke said trading had continued as usual in all stores but the owners of about 250 cars had not been able to return to their vehicles.

Ms Clarke said the centre was providing free beverages to people unable to access their cars at two cafes designated as waiting areas.

The centre closed at 6pm.

Police were unable to comment on when the carpark would reopen.