CÚCUTA, Colombia -- At a border checkpoint between Venezuela and Colombia, luggage is the easiest way to spot Venezuelans looking for a new life, reports CBS News correspondent Manuel Bojorquez.

Marcos Gonzales crossed into Cúcuta, Colombia, with his wife and son. "A lot of pain," he said. "This is real life."

Tens of thousands of Venezuelans cross into Colombia -- even just for the day -- in search of food and work. Now, they're fleeing deadly fighting between the Venezuelan military and protesters, who blame the government for the country's economic collapse.

Venezuela's president refuses to back down, even in the face of further U.S. sanctions. The opposition vows a nationwide strike on Thursday, setting the stage for even more unrest.

Jose Oropeza fled Venezuela two months ago, leaving behind his wife and two children because he feared becoming a political prisoner.

Jose Oropeza CBS News

"Why are you part of the resistance?" Bojorquez asked.

"Because I see children who have nothing to eat, people who are hungry, the elderly knocking on my door for coffee or food," Oropeza said.

Medicine is also in short supply. On the Colombian side of the border, Cúcuta's main hospital used to see one or two Venezuelan women a week for prenatal care. Now it's up to five or six a day.

Some have crossed to give birth.

"We can't keep treating Venezuelan patients and not being reimbursed," said Dr. Juan Montoya, the hospital's general manager.

But they keep coming, not knowing when they may be able to cross that bridge back home.