BEIJING, Aug 4 (Reuters) - Rain pelted swathes of China's biggest grain producing province on Friday, submerging farms and worsening floods that have already swamped cities around the country as rescue workers scramble to contain the havoc caused by Typhoon Doksuri.

Northeastern Heilongjiang, known as China's "great northern granary", is the latest area to suffer the aftermath of Doksuri, which has killed at least 20 people, displaced thousands and flooded Beijing and several other cities since it made landfall in the south a week ago.

In Heilongjiang, authorities warned residents to expect more severe weather, including tornadoes, and raised the flood alert twice since Thursday night. Some areas could see more than 100mm (3.9 inches) of rain in a few hours, they added.

China's oldest and biggest oilfield in Daqing is also located in Heilongjiang.

In the waterlogged provincial capital Harbin, two vehicles plunged into a sinkhole that appeared on an expressway near a swollen river, local media reported. Paddy fields have also been inundated, and villagers in low-lying areas told to evacuate, local media reported.

A widely shared video on social media showed a goat stranded on top of a rooftop and a pig trying to swim against the flood torrents.

The storms and floods also triggered power cuts in nearby Shangzhi city, where supermarkets were running low on provisions, according to media reports. "I only managed to get a few bottles of mineral water and two boxes of instant noodles," a Shangzhi resident told local media after rushing to the supermarket after the storm alerts.

Further south, in the corn-growing region of Jilin, authorities have set up camps for the 12,550 people evacuated from Shulan city, where as much as 484.7 mm (19 inches) of rain have fallen over the past three days, state media reported.

INVESTORS SEEK ANSWERS

The widespread flooding across China has damaged agricultural land and industrial areas, triggering anxious investors to seek more information from companies listed on local stock exchanges.

Chinese maker of aerospace products Aerospace Hi-tech Holdings Group Co said the factory of a unit in Zhuozhou, Hebei province, had been flooded.

"Some production and power equipments were damaged, and production had been suspended," the company said in an exchange filing on Friday.

Zhuozhou city, in northern Hebei province, saw more than a year's worth of rainfall just this week.

Qinghai Jinrui Mineral Development Co, a producer of chemical products, said flooding at a factory in Chongqing had triggered an emergency suspension of production.

The affected production facility is a main source of revenue, so the disaster would impact the company's performance this year, Jinrui said in a statement.

(Reporting by Liz Lee, Ella Cao, Samuel Shen, Ryan Woo, Beijing and Shanghai newsroom. Editing by Gerry Doyle and Miral Fahmy)