Fines will only be imposed on people riding motorcycles without helmets－not those riding electric bikes－in a nationwide campaign starting on June 1, the Ministry of Public Security's Traffic Management Bureau announced on Thursday.

That could put an end to hikes in electric bicycle helmet prices that started this week in many parts of the country.

The bureau said electric bike riders and passengers who don't wear helmets will not be fined, but helmet safety promotions will be carried out nationwide. Motorcycle riders who don't wear helmets could face fines of up to 200 yuan ($28).

On Wednesday, the ministry also said that it will investigate the ongoing price hikes of electric bicycle helmets, which have been in high demand since the ministry announced in mid-April that it would enforce helmet wearing among riders starting in June.

Increased demand for helmets has led to skyrocketing sales and prices over the past week.

The ministry said on its WeChat instant-messaging account that it has contacted the country's market supervision authority and will team up with local police to crack down on illegal price hikes of safety gear.

On the Taobao e-commerce platform, the first 15 products that pop up in response to a search for "electric bike helmet" each recorded sales of more than 10,000 helmets over the past month.

The top sales for women's helmets on the platform came from an online shop based in Wenzhou, Zhejiang province, with more than 80,000 sales over the past month.

Some buyers left comments saying that a product currently priced at 99 yuan was selling for around 20 yuan a month ago.

On JD.com, another e-commerce platform, most of the best-selling helmets were priced at more than 200 yuan, with those for children priced at around 100 yuan.

Ying Zi, who sells daily necessities via links on WeChat as a side job, said she began selling helmets on Monday and sold "an incredible" 30 helmets that day.

"I'm still sharing purchase links of helmets. The price has risen from 69 yuan to 89 yuan," said Ying, the manager of a housekeeping agency in Shanghai, adding that many housekeepers relied on electric bicycles for their daily commute.

Electric bicycles have become one of the most popular commuting vehicles in the country, with 250 million on the roads in 2018, according to the China Association of Bicycles.

Police said electric bicycle are involved in a large number of traffic accident fatalities, and 80 percent of the victims in such accidents died of brain injury.

Police cited research showing that wearing qualified helmets properly when riding an electric bicycle can reduce the risk of death from a traffic accident by at least 60 percent.

In Shanghai, awareness campaigns and helmet safety promotions have included lectures for enterprises providing express delivery services and putting posters in stores selling electric bikes, Shanghai traffic police said.