The recently concluded Zimbabwe tri-series has come under a match-fixing cloud as two International Cricket Council Anti-Corruption Unit personnel arrived in New Delhi on Monday to investigate the links between six bookies in the city and players involved in the series.

The ACU officials, Martin Hawkins and Allen Peacock, were reportedly tipped off by their colleagues supervising the series.

Two things -- India's below-par performance and New Zealand dropping strike bowlers Shane Bond and Daniel Vettori against India in the fifth game of the series -- have fanned ACU's doubts.

The fourth one-day international during Pakistan's tour of India, where the game in Ahmedabad was delayed due to wet pitch conditions, is also under the ICC scanner.

The first Test match between India and Zimbabwe commences on Tuesday in Bulawayo at 1300 hours, IST.