The Archaeological Survey of India (ASI) has begun extensive repair work on one of the four minarets of the iconic 17th century monument of love, the

The ASI has undertaken the exercise after reports of damage and cracks in the stones and rusting of iron clamps.

ASI chief in Agra, Vasant Swarnakar told IANS that this was a "special exercise" and not a routine one. Soon scaffolding would soon be erected and the area fenced to keep visitors at a safe distance.

Officials said this repair work to replace damaged stones and fix lining in black stones that had peeled off was being undertaken after almost 90 years. Around two dozen marble slabs of the stairs would be replaced.

The dome of the main mausoleum will also be given mud pack treatment to contain "discolouration" and cleanse the yellow stains. This "beauty parlour treatment" is now a regular feature, to ensure the world heritage monument appeared sparkling white.

Meanwhile, the greenish patches on the white marble stones at the rear, towards Yamuna, have appeared again as bacterial colonies have developed in the highly polluted water of the river. Tiny insects identified as Goeldichironomus, feeding on pollutants, leave their poo on the surface, giving a green look, according to experts.