The talented Richa Mishra continued to make waves in the pool, setting her second record of the meet, as four national records fell by the wayside in the 57th National Aquatics championships in Kolkata on Thursday.

Mishra, who created a new record in the 50 metres butterfly on Wednesday, extended her good show in the 400 metres medley, setting a new mark on course to a golden finish.

The 21-year-old lass, who is turning out for Police Sports Control Board, swam the distance in 5:08.57 seconds to dock about six-and-half seconds from her own existing mark of 5:15.28 seconds, posted in the 2000 meet.

Mishra established an early lead and finished at least 10 metres ahead of Kanrnaka girl Ambica Iyengar, who had to remain content with the silver after registering a timing of 5:20.79s.

Karnataka, who won three golds along with PSCB during the day, tasted their second success in the women's 50m freestyle, where Sikha Tandon justified her top billing to set a record with a timing of 26.61 seconds, thereby qualifying for the Athens Olympics.

Tandon had attained the Olympics qualifying mark of 26.92 second in July by virtue of her timing in the first lap of the 100m freestyle event at the World Championships in Barcelona.

Tandon was on a song during the day as she first erased the record sety by Nisha Millet (28.01s) in 1997, clocking 27.57 seconds in the heat, before bettering her performance in the final.

It was a one-two for Karnataka as Reshma Millet, sister of the celebrated Nisha, finished second with a timing of 28.07 seconds. PSCB's Rishu Mehra claimed the third spot (28.90s).

Another national mark was set, in the women's 800m freestyle relay, when the Karnataka quartet of Ambica Iyenger, the Millet sisters - Nisa and Reshma - and V Shivaranjani traversed the distance in 9:01.27s, obliterating the old record of 9:06.29s, set by the participants of the same state in 1998.

PSCB (9:32.98s) claimed the silver, while Kerala (9:48.06s) bagged the bronze.

The only men's record came in the 800m freestyle relay where PSCB swimmers won the gold, finishing in 8:13.38s.

The four-member team of Dipak Kumar Singh, Kailash Nath and the Muralidharan siblings - Arjun ane Amar - erased the old mark of 8:15.60s, created by the Railway Sports Control Board swimmers in 2000.

The silver went to the Services Sports Selection Board (8:15.82s), while Railway Sports Control Board (8:25.35 s) claimed the bronze.

After two days, PSCB lead the medal tally with six golds, while Karnataka are now a close second with five.

In the men's 400m individual medley, Karnataka's Srinand Srinivas won the gold, clocking 4:51.30s, leaving behind PSCB's Arjun Muralidleran (4:52.00s) and SSCB's Nilendu Jena (4:56.90s), who got the silver and bronze respectively.

The 50m breaststroke gold was pocketed by PSCB's Deepak Kumar Singh with a 30.43 seconds finish, while Gairik Bardhan picked the silver (31.1 seconds) to earn the day's only medal for hosts Bengal.

Puneet Rana of Punjab claimed the bronze, touching the finishing pad in 31.49 seconds.

T A Sujith of SSCB (24.23s) garnered the only gold for the military side in men's 50m freestyle, with the silver going to Maharashtra's Varun Divgikar (24.56s).

The event proved lucky for SSCB, as Saiju Joseph took the bronze (24.61s).

In highboard diving, RSCB's Sachin Tripathy got the men's gold with 438.95 points, while the women's honours were secured by RSCB's Mamoni Mandal, totalling 337.30 points.