Guwahati, June 4: A freak blast blew the lid off the United Liberation Front of Asom’s operations in the city today.

Explosives stored in junior railway engineer Tapan Deka’s quarters went off by accident around 8.30 am, leading police to detain the official, his son and daughter.

After neighbours informed them of the blast, the police found 1.9 kg of RDX and 250 gm of TNT ? enough to make several powerful bombs ? from a concealed underground pit in the backyard of the East Gotanagar house.

A search of the house led to the discovery of 10 9mm pistol cartridges from the make-up box of Deka’s daughter, Dolly, a higher secondary student.

Photographs of senior Ulfa leader Biju Chakraborty in the Dekas’ family album deepened suspicions about the family’s links with the rebel outfit.

Biju Chakraborty, a self-styled Ulfa lieutenant, is believed to have been involved in the serial blasts that rocked the city in March.

Officers also claimed that a slain Ulfa leader, Utpal Das alias Milkha Singh, had stayed with the Dekas for about a month before he was killed in an encounter with the police at Lokhra recently.

City police spokesperson and additional superintendent of police Bibekananda Das said the bomb that exploded was also concealed underground. Explosives experts visited the spot to determine the cause of the blast.

Deka and his son Ridip, a student of Cotton College, were detained to find out the family’s links with the Ulfa. The police believe militants frequently used Deka’s government quarters as a hideout during their operations in the city.

Police sources said the father-son duo is likely to be arrested.

Dolly told the police she did not know that live bullets had been kept inside her make-up box which, she said, she hadn’t opened for quite some time.

Some dry cells, bicycle ball-bearings and other articles used for making crude explosives, as well as some technical drawings relating to bomb-making, were also found.