(Update as of 1336 EST)

A reactor cooling system malfunctioned at the Fukushima Nuclear Power Plant in Japan on Friday, prompting the country to declare a nuclear emergency in the aftermath of the large earthquake.

However, there was no information about a leak or contamination at any of Japan’s eleven reactors, according to Prime Minister Naoto Kan.

Kan told a press conference, “Regarding our nuclear power facilities, so far no radioactive material has been leaked to the outside. Given the situation, an emergency disaster response has been set up as myself as a head. We will secure the safety of the people of Japan. We ask the people of Japan to act calmly.”

Late on Friday, Japan’s nuclear safety agency said pressure inside the reactor at the Fukushima No. 1 power plant in northern Japan had risen to 1.5 times the level considered normal. To reduce the pressure, officials were considering releasing slightly radioactive vapour, the Associated Press reported. The agency said the radioactive element in the vapour would not affect the environment or human health.

Earlier in the day, the government had declared a nuclear power emergency situation, which occurs if there is confirmation of radioactivity leaks from a nuclear power plant or a reactor cooling system breaks down.

In this case, it seems to be the latter, as Dow Jones reported that Tokyo Electric Power Co had filed an emergency report with the government Friday in which it said it faces a shortage of capacity to cool its reactors at Fukushima Nuclear Power Plant.

The reactors at Fukushima should have multiple, redundant safety features installed to help cool reactor cores and prevent meltdown so its unclear what the company means by a “shortage of capacity.” The eight reactors at Fukushima are “boiling water reactors,” which means the reactor needs to be cooled after fission stops following emergency shut-down. To do this, water must be pumped into the reactor core; but that requires electricity, and press reports in Japan suggested that a back-up diesel generator at the plant had failed. Should the coolant system fail, meltdown can occur and, should containment systems fail, a radioactive plum could explode from the power plant as it did in Chernobyl in 1986.

Hillary Clinton said the U.S. had assisted in the emergency by sending coolant to the plant. “We just had our Air Force assets in Japan transport some really important coolant to one of the nuclear plants,” Clinton said, according to Reuters. “You know Japan is very reliant on nuclear power and they have very high engineering standards but one of their plants came under a lot of stress with the earthquake and didn’t have enough coolant.”

After Clinton’s announcement and late on Friday, Japan’s Chief Cabinet Secretary Yukio Edano told reporters that people within 2 to 3 kilometers (1.2 to 1.8 miles) of the Fukushima Daiichi power plant have been told to leave the area. Those closer by — within 3 to 10 kilometers — were asked to stay home. Japan’s Kyodo News Agency estimated that the evacuation order directly affected about 3,000 people. “This is a precautionary instruction for people to evacuate,” Edano said, according to CNN.

Yet Edano also said the Fukushima Daiichi reactor “remains at a high temperature,” because it “cannot cool down.”

Japan has long faced fears over the safety of its nuclear reactors given their location on top of four seismic plates—and public confidence in nuclear power dipped in 2007 when an earthquake caused a radiation leak in Kashiwazaki Kariwa nuclear plant. As Toko Sekiguchi reported for TIME, there were recriminations following the quake between plant operator Tokyo Electric and the government, which accused the company of failing to respond quickly enough in the quake’s aftermath. The President of the company apologized–though the IAEA later found that the Kashiwazaki Kariwa plant “behaved in a safe manner, during and after the earthquake.”

This time, at least, there seems to have been more open and swift communication between Tokyo Electric and Japenese and international officials. The IAEA said on Friday that it had been alerted of a heightened state of alert at Fukushima and was following the situation.

Stay tuned to Ecocentric for updates.