New Delhi, Sep 24 - Old grenades are proving to be a problem area for the Indian Army, the officer responsible for maintaining quality assurance admitted Thursday.

'They (the grenades) are very old. They are of vintage quality and we are looking into it,' Lt. Gen. J.S. Dhillon, who heads the Directorate General of Quality Assurance (DGQA), told reporters here.

There have been reports of late that 30 percent of the grenades used in counter-insurgency operations fail to explode. Others take up to four seconds to explode -- 1.5 seconds longer than those used by militants.

The defence ministry has sought an immediate report on this.

'The grenades are very old. The detonators' shelf life is over, creating the problem we have in hand,' another senior Indian Army official told IANS, requesting anonymity.

The DGQA, in association with the Defence Research and Development Organisation (DRDO), has finalised the design for a new grenade to resolve the problem.

'The new design by DRDO is already in place and hopefully it will soon be operational,' Dhillon added.