Thousands of illegal workers have been rushing to leave Malaysia, as a deadline to get out of country expired.
The deadline expires at midnight local time
Thousands more are in hiding, saying that the government's crackdown leaves them with no jobs to go home to, or complaining that they are owed wages.
The authorities have put armed volunteer reservists on standby for the launch of a huge operation to deport those who choose to stay behind.
Punishments could include heavy fines, jail sentences and whipping.
The deadline for illegal workers to leave Malaysia has been extended three times since the policy was first announced in October, but despite this, the Malaysian immigration authorities estimate that at least 200,000 illegal workers remain.
The Malaysian government says it has recruited more than 300,000 volunteers to round up those who stay.
They will be paid cash rewards for each illegal worker they apprehend.
Members of the public are being invited to ring a special hotline to report suspect foreigners to the authorities.
400,000-600,000 foreigners have already left
At least 200,000 remain
Many work in construction, plantations and domestic service
They risk jail, fines and whipping if found
Throughout the day, crowds of people have queued at a ferry port near the capital, Kuala Lumpur, to board ships and naval vessels bound for Indonesia.
Hundreds more waited outside the United Nations refugee agency in Kuala Lumpur, hoping to be given papers that, in theory, could exempt them from deportation.
"I feel sad leaving, but I don't want to be whipped or jailed," said Mohamad Sifud, 30, who has worked illegally in construction for 10 years.
Foreign labourers without papers are being offered the chance to come back if they acquire the proper documentation.
"I will definitely come back legally," Mohamad Sifud told the Associated Press. "There is not much work back home."
But not everyone will be confident that they will be able to get a job legally.
Alia Shukri, from Bali, said she would stay put.
"People ask me many times am I not afraid of being caught and jailed," she said. "Yes, I am scared, but what choice do I have?"
Most of the illegal workers are Indonesian, and the 26 December Indian Ocean tsunami and interventions by the government in Jakarta have prompted the Malaysian government to delay the crackdown three times before.
Indonesia's Labour Minister, Fahmi Idris, told a Malaysian news website that 100,000 Indonesians are refusing to leave because they are owed wages, and that his government would take legal action unless they were paid.
Malaysian Interior Minister Azmi Khalid stressed that he wanted the deportations to be carried out humanely.
But human rights groups say the involvement of poorly-trained volunteers carrying firearms invites accidents.
Those illegal workers who have not left by midnight local time will be banned from returning, and could also face two years in jail, fines of $13,000, and, for anyone under 50, up to six strokes of the cane.