Anushree Fadnavis/Reuters Police officers stand by as migrant workers scramble inside a bus station in Ghaziabad, India, on Saturday, March 28. Mass exodus sparks coronavirus concerns in India

Anushree Fadnavis/Reuters Police officers stand by as migrant workers scramble inside a bus station in Ghaziabad, India, on Saturday, March 28.

Tens of thousands of migrant workers fled India's largest cities this weekend, looking to return to their rural homes after a nationwide lockdown left them without jobs or pay.

The lockdown was put in place to try to slow the spread of the novel coronavirus. But there is concern that the migrants' mass exodus may have done the opposite.

On Sunday, Prime Minister Narendra Modi urged all states to seal their borders to stop the virus being imported into rural areas. Officials are now scrambling to find migrant workers who had already returned to small towns and villages across the country, in order to quarantine them for 14 days.

Every year, more than 9 million migrant workers move from India's rural areas to large population centers to find work at construction sites or factories, sending money back to their hometowns and villages.