Shares of country's leading automobile companies Tata Motors and Maruti Suzuki India plunged as much as 2.5 per cent on Monday after both companies posted the sales results for April. At 2:36 pm, stocks of Tata Motors were down 1.6 per cent at Rs 430, and stocks of Maruti Suzuki plunged 1.4 per cent at Rs 7,622, respectively.