Tens of thousands of people have placed orders for free potassium iodide pills in the days following a false alert from the province about an incident at a nuclear plant in Pickering, Ont.

Sunday's alert, which was sent to mobile phones across Ontario, shocked those within a 10-kilometre radius of the Durham Region plant and even those living farther away.

About an hour after the 7:24 a.m. ET alert, Ontario Power Generation (OPG), the plant's operator, tweeted without explanation that the warning "was sent in error." The Ontario government also later acknowledged the mistake, blaming human error, and issued an apology.

Although the mistake left some people fuming, others stepped up their planning for a real emergency.

Between Sunday morning and Monday afternoon, 32,388 orders were placed for potassium iodide tablets through Durham Region's Prepare To Be Safe website, which is jointly managed by the City of Toronto and OPG.

Typically, OPG says, between 100 and 200 orders are placed per month.

The pills can be ingested to protect the thyroid gland from radioactive iodine that could be released into the air in a nuclear emergency.

In small quantities, it is an "essential nutrient for your thyroid gland to function properly," and is "effective in reducing the threat of thyroid cancer to residents at risk of inhaling or ingesting radioactive iodine," according to the Canadian government's website.

The pills are distributed automatically to homes and businesses within 10 kilometres of every nuclear power plant in Ontario.

Depending on residents' postal codes and road boundaries, people within 10 to 50 kilometres of a plant in the province can order tablets free through the Prepare To Be Safe website.

OPG told CBC News that the majority of orders come from people in the Greater Toronto Area.