An SMS warning about explosions at five places in the city, including two railway stations, turned out to be hoax after searches in all the areas failed to yield anything, police said on Sunday.
Extensive searches were carried out in all these places by a bomb disposal squad, aided by sniffer dogs, but they did not find anything, a top police official said.
He said police had traced the origin of the SMS and found that three college students had sent it, "but without any ulterior motive". The trio, on being questioned, said they had sent the SMS just to warn people, he said.
The SMS said bombs would explode at five places -- Oberon Mall in the outskirts of the city, Ernakulam South and North railway stations, Greater Cochin Development Authority office and another mall at Menaka in the heart of the city -- before March 16.
The message was received by an officer, who passed it on to the police official. Earlier reports had said police were alerted by a journalist, who was informed of the threat by a woman who received the SMS.
Kochi and surrounding areas have been put on high alert and security increased in important areas and installations after an intelligence input of a LeT threat.