"We have suspended the inspector-in charge Shyamvrat Yadav along with two constables who were on duty that day as they failed to solve the case within the stipulated time," SP GRP P K Singh said.
Inspector Yadav was given two days time to solve the case, he said, adding a fresh team of GRP officials have been deployed to probe the case.
Armed men on Wednesday struck three trains -- Lucknow-LTT Express, Vaishali Express and Lucknow-Kanpur passenger train -- and robbed at least 12 passengers in the wee hours between Unnao and Kanpur districts.
GRP is also conducting raids to nab the culprits, he added.