The two guards let in the constables who visited the mall as decoys without proper checking and failing to detect that they had pistols tied to their ankles.
The guards were arrested and later released on bail after registering a case for negligence under the IPC against them, said Rajendra Kulkarni, senior inspector of Parkside police station in Vikhroli.
"Considering the terrorist attacks in Punjab and the city being on high alert, we have tightened vigil in our area," Kulkarni said.
More such check would be carry out in the city in coming days, Kulkarni said.