More than three days after the blasts, the authorities have still been unable to identify the toxic chemicals smoldering at the site of the destroyed warehouse, a temporary depot for substances that are some of the chemical industry’s most volatile and toxic.

On Saturday, Chinese news outlets reported that a customs authority inventory did not match the list of stored goods provided by Rui Hai employees, suggesting that the company may have been illegally transporting chemicals. “Some relevant people indicated that the differences in the information point to the possibility of smuggling,” the newsmagazine Caijing wrote on its website.

Investigators have so far confirmed only the presence of sodium cyanide, a highly toxic substance that has already seeped into drainage pipes beneath the port facilities. A report in The Beijing News said Rui Hai had been illegally storing some of the chemicals outdoors in “metal buckets and wooden crates.” Another report in the state-run Science Daily newspaper said there were at least 700 tons of sodium cyanide at the site, far in excess of the 10 tons it was licensed to handle. The chemical, which is used in the mining of gold, is extremely lethal in tiny amounts and can release a deadly and flammable gas.

Experts have expressed concern about forecasts of rain, saying precipitation could spread the contamination beyond the immediate blast zone. In addition to sending a team of hazardous materials experts, the authorities have been trying to prevent rain from falling on the area, the state media said, presumably by firing silver-iodide rockets into approaching storm clouds.

Among those reportedly sent to help identify the chemicals were employees of the agency that manages the sprawling port. In a posting on WeChat, a popular messaging app, one man expressed alarm that his wife and her co-workers were being trained to survey areas outside the disaster’s epicenter for stray chemicals.

“It was ordered by the chairwoman of Tianjin Port, who is betting the health and lives of ordinary employees just for her political career,” wrote the man, who declined to give his name during a brief phone conversation, saying he did not want to endanger his wife’s job.