Barring the stabbing incident, the situation in the areas was under control and peaceful, Gujarat Minister of State for Home Haren Pandya told reporters here.

Pandya said an investigation would be conducted to ascertain the cause of the violence.

He said 18 persons including six policemen were injured in stabbing and stone throwing incidents last night.

Pandya said police had burst 423 teargas shells and fired 60 rounds in the air to contain the roiting mobs.

Seven cases have been registered in four police station areas and 31 persons involved in the violence arrested.

Twenty companies of SRP and four of RAF had been deployed in the curfew-bound areas, he said.

Trouble started when a scuffle between two local youths over``teasing of a mentally retarded person'' escalated with rival groups pelting stones at each other, Pandya said.

A meeting of leaders of both the groups was held in Ahmedabad to initiate steps to restore peace, he said adding all the leaders had agreed to cooperate with the authorities and appeal to people to exercise restraint.