The iPhone manufacturer Foxconn has reopened a factory in India which was shut down temporarily when 250 workers fell sick, sending its shares up 9%.
The plant in Madras (Chennai), which makes mobile phone parts, was closed last Monday after workers complained of nausea and giddiness.
Work resumed on Saturday after the firm received clearance from the government.
Working conditions at Foxconn factories have caused concern, after a string of suicides this year at a plant in China.
The company has said it is taking the deaths seriously, even though a local government investigation did not blame working conditions.
Foxconn is owned by the Taiwanese group Hon Hai Precision, the world's largest maker of consumer electronics, and employs 800,000 workers worldwide.
All of the workers in the Madras factory who complained of illness were taken to hospital.
"All our workers who had any health complaints have seen a doctor, and the local authorities have also given us the go-ahead to resume operations," Vincent Tong, a senior director at Foxconn said.