BOGOTA (Reuters) - More than a million people have left Venezuela to live in Colombia during the last 15 months, with arrivals expected to continue, the Colombian government said on Wednesday, as its socialist neighbor suffers a deep economic crisis.

A two-month national survey to track migrants showed 442,462 Venezuelans without visas, stamped passports or temporary permission to remain had arrived over the 15 months. Another 376,572 arrivals did have legal permission.

In addition, some 250,000 Colombian citizens who had been living in Venezuela also returned home during that period.

“More than a million people have migrated from Venezuela to Colombia in the last 15 months, of which 250,000 are returning Colombians and 819,000 are Venezuelans with the intent to stay,” Felipe Munoz, the Colombian government’s director of border issues told journalists.

Colombia had asked Venezuelans to register if they do not have work or tourism visas, dual citizenship, or some other type of formal permission to remain in Colombia. The government has said the information is meant to help understand resources needed for schooling, medical care and other services.

Undocumented Venezuelans who did not register in the census will be subject to deportation, Christian Kruger, the head of the migration agency said.

“Clearly while Venezuela’s problems in terms of food and health continue, these figures are going to keep growing. We can’t think it will end,” Kruger said.

Estimates of how many Venezuelans have left their home country during the tenures of former President Hugo Chavez and current leader Nicolas Maduro vary widely, with some opponents and academics putting the figure at 4 million. Maduro, who won re-election last month, insists that is an exaggeration.