As U.S. states lift COVID-19 lockdowns and many more states ease restrictions, experts are warning of a possible increase in new cases. 

Some states are already reporting new infections. 

Alabama, South Dakota and Texas have already seen a rise in COVID-19 cases, according to Dr. Scott Gottlieb, the former Food and Drug Administration Commissioner.

He says many states are easing restrictions despite failing to meet reopening criteria set by the White House. 

It could also take several weeks, or more, for states to report increases in infections, in part, because of how long it can take infected people to develop symptoms.

In Colorado, the regional health department shut down a restaurant after it defied the governor's "Safer At Home" order and packed hundreds of customers into its dining room on Mother's Day.

According to video from a local reporter, nearly every table in the restaurant was full. Customers crowded around a counter to place orders and the line to get inside wrapped around the side of the building. The video also showed few people wearing masks.

Reports of crowded spaces and upticks in COVID-19 cases are not limited to the U.S.

In Paris, police cleared the banks of the Seine river and the city's popular Canal St.-Martin, after crowds gathered to celebrate the end of an eight-week lockdown.

And in London, a podcaster posted on Twitter, a video showing a crowded bus.

South Korea, Germany and China also have reported new cases, creating concerns over a possible second wave of infections in these countries.

"We must never lower our guard regarding epidemic prevention," said South Korean President Moon Jae-in, after new cases were reported in the country's capital Seoul.

The city of Wuhan, where doctors first reported an outbreak of COVID-19, is re-testing all 14-million of the city's residents after discovering six new cases. These were Wuhan's first new cases in more than a month. 

German states and the federal government agreed to reinstate COVID-19 lockdown measures if any German county exceeds 50 new cases per 100,000 inhabitants.

CNN reports that over the weekend several German counties passed that limit.

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