Munoz had a 6-under-par 66 and Nordqvist was one of four golfers to turn in a 68 in fashioning 36-hole totals of 7-under 137.
Four other golfers are tied at 4-under 140.
Ai Miyazato, who was tied with Tseng for the first-round lead, shot 1-over 73 in the second round and dropped into a tie for ninth at 3-under overall.
Munoz had a string of three bogeys in Thursday's round but was bogey-free in the second round. She had had a birdie at the fifth hole and an eagle at the par-5 sixth hole. She closed out the front nine with a birdie at No. 9. Back-to-back birdies at 12 and 13 have her tied for the lead.
Nordqvist had five birdies and a bogey at the eighth hole Friday. She had birdies at Nos. 9, 15 and 18, which were among the holes she birdied Thursday.