* Japan min: China says no rare earth export ban to Japan
* Japan min: Heard from trading firms exports are blocked (Recasts, adds comments from trade minister)
TOKYO, Sept 24 (Reuters) - Tokyo has heard from some trading companies that rare earth exports to Japan from China have been blocked, but China has told it that there is no such ban, Japan's trade minister said on Friday.
The comment comes after a New York Times report that China has banned exports of rare earth metals to Japan, the latest development amid heightening tensions between Asia's two biggest economies.
The two sides are locked in a dispute over Japan's detention of a Chinese fishing boat captain whose trawler collided earlier this month with a Japanese patrol boat, while Japan confirmed on Friday that four Japanese nationals had been detained in China on suspicion of violating Chinese law.
"China has not done anything like an official embargo. That's what we've heard from China's trade ministry," Akihiro Ohata, head of the Ministry of Economy, Trade and Industry, told reporters on Friday.
"We've heard from trading firms that (the reported rare earth export suspension) is happening, so we're checking what's going on," he said.
A Chinese trade official on Thursday denied the New York Times report.
The report, which was sourced to unnamed industry experts, said an initial trade embargo on all exports of rare earth minerals would last through the end of this month.
Rare earth elements have a variety of technological and industrial applications. (Reporting by Risa Maeda; Editing by Chris Gallagher)