BEIJING (Reuters) - Shanghai increased airport screening on Saturday as imported coronavirus infections from countries such as Italy and Iran emerge as the biggest source of new cases in China outside Hubei, the province where the outbreak originated.

FILE PHOTO: Community workers in protective suits disinfect a residential compound in Wuhan, the epicentre of the novel coronavirus outbreak, Hubei province, China March 6, 2020. REUTERS/Stringer

Mainland China had 99 new confirmed cases on Friday, according to official data. Of the 25 that were outside Hubei, 24 came from outside China.

Shanghai, which had three new cases that originated from abroad on Friday, said it would step up control measures at the border, which had become “the main battlefield”.

At a news conference, Shanghai Customs officials said they city would check all passengers from seriously affected countries for the virus, among other airport measures.

Shanghai already requires passengers flying in from such countries, regardless of nationality, to be quarantined for 14 days. They will now be escorted home in vehicles provided by the government.

Tighter screening has greatly lengthened waiting times at Shanghai’s Pudong International Airport - some passengers say they have had to wait as long as seven hours.

The Shanghai government vowed on Saturday to severely punish passengers who concealed infections.

Beijing police said on Saturday they would work with other departments to prevent imported infections. They said some members of a Chinese family flying in from Italy on March 4 had failed to fill in health declarations accurately, and later tested positive for the virus.

MIGRANT WORKERS

In addition to the growing risk of imported infections, China faces a challenge in trying to get migrant workers back to work by early April.

So far, 78 million migrant workers, or 60% of those who left for the Lunar New Year holiday in January, have returned to work.

Yang Wenzhuang of the National Health Commission (NHC) said that the “risk of contagion from increased population flows and gathering is increasing ... We must not relax or lower the bar for virus control”.

But new cases in mainland China continued to decline, with just 99 new cases on Friday, the lowest number the NHC started publishing nationwide figures on Jan. 20, against 143 on Thursday.

Most of these cases, which include infections of Chinese nationals who caught the virus abroad, were in the northwesterly Gansu province, among quarantined passengers who flew into the provincial capital Lanzhou from Iran between March 2 and 5.

For the second day in a row, there were no new infections in Hubei outside the provincial capital Wuhan, where new cases fell to the lowest level since Jan. 25.

The total number of confirmed cases in mainland China so far is 80,651, with 3,070 deaths, up by 28 from Thursday.

Hubei reported 28 deaths, 21 of them in Wuhan.