Three national records tumbled as Police Sports Control Board bagged three gold medals on the opening day of the 57th National Aquatics Championships in Kolkata on Wednesday.

Putting behind her injury and weight blues, 21-year-old Karnataka girl Nisha Millet claimed the honours in the women's 400m freestyle, setting up a new national mark while finishing the race in 4:33.55 seconds.

She eclipsed the old record of  state mate Sikha Tandon, who had clocked 4:38.04 seconds in 1998.

Karnataka's V Shivaranjani, who participated in the World Championships in Barcelona, had to remain satisfied with a silver, with a timing of 4:41.16 seconds, while Police's Bhawana Sharma bagged the bronze in 4:51.43 seconds.

Millet, who is participating in the National championships after a five-year hiatus, was satisfied with her timing. She said the victory boosted her confidence for upcoming events, the immediate being the Afro-Asian Games.

Soon after winning medals galore at the Imphal National Games in 1999, Millet was laid low by a painful, benign tumour on her back which required surgery. To add to her woes, she put on an extra ten kilos but got into shape only this year after a stint in Australia.

The talented Richa Mishra of PSCB then made a big splash in the pool, eclipsing a five-year-old national record in the women's 50m butterly, with a 30.55 seconds finish to take the gold. The old record was in the name of Karnataka's Meghna Narayan, who had clocked 30.57 seconds in 1998.

Mishra, who hails from Delhi but now works for CRPF, later said that a four-month stint in Hungary under the celebrated Otto Kovacs had done wonders for her.

Karnataka's C Subha (30.67s) and B Praveena of Kerala (32.73s) won the silver and bronze medals respectively.

The sole men's record came in the 50m butterfly event final where Kerala's K Rajiv showed sparkling form to better his own national mark, set in the heats in the morning.

Rajiv, who had clocked 26.37 seconds in the heats to erase the existing record of 26.44 seconds by Shane Pedder of Maharashtra in 1998, later performed even better in the final, registering a timing of 26.27 seconds to ensure the only gold for his state at the Subhas Sarobar swimming pool.

Earlier, Mandar Anand Divase displayed fine endurance to give PSCB its first gold by winning the 400m freestyle.

Divase completed the eight-lap race in 4:13.33 seconds to push team mate and national record holder Kailash Nath (4:16.41s) and Services Sports Control Board's Terismon Thomas (4:21.91s) to the silver and bronze respectively.

In the men's 100m backstroke, PSCB's T K Senthil Kumar (1:01.98s) bagged the yellow metal while Railwayman Dipesh Bairagi (1:02.21s) got the silver and Services's Joshy Joseph (1:04.12s) earned the bronze.

Karnataka clinched their second gold of the day in women's 100m breaststroke, with Ambica N S Iyengar clocking 1:19.93s.

Bhavana Sharma of PSCB had to be content with the silver while the bronze went to another Karnatak lass, D Mrudula.