The Islamic State is building and deploying improvised explosive devices on a “quasi-industrial scale” across Iraq and Syria, according to a new report that examines the group’s supply chain.

The organization has utilized bomb components that were manufactured in 20 countries across four continents, Conflict Armament Research said last week in a report on its 20-month study.

The bombs have become the organization’s “signature weapon,” according to the report, in large part because they can be built out of inexpensive components that can easily be purchased.

The report notes many IED parts are commercial goods like fertilizer, cell phones and other electronic elements, the sale of which aren’t as tightly scrutinized and regulated as firearms. That has allowed more than 700 items connected to Brazil, China, Switzerland, Japan, the United States and 15 other nations to end up in the Islamic State’s improvised explosive devices.

The study indicated 13 Turkish companies were connected to the supply chain, the most of any nation. India followed with seven companies and the United Arab Emirates was third with six.

The report does not accuse any of the 20 countries, or the 51 companies, of directly supplying the material to the Islamic State. It notes that all of the products were lawfully obtained by trade and distribution companies, who subsequently sold them to smaller commercial outlets.

Many of those smaller entities “appear to have sold, whether wittingly or unwittingly” the items to people in some way associated with the Islamic State, the report states, adding that those smaller sellers “appear to be the weakest link in the chain of custody.”

Conflict Armament Research found the Islamic State was able to obtain some products shortly after they were legally given to commercial entities, suggesting some issues with the process.

“The appearance of these components in possession of IS forces, as little as one month following their lawful supply to commercial entities in the region, speaks to a lack of monitoring by national governments and companies alike,” the report states. “It may also indicate a lack of awareness surrounding the potential use of these civilian-market components by terrorist and insurgent forces.”

Islamic State terrorist attacks killed 6,073 people in Iraq, Syria, Egypt, Lebanon and Turkey in 2014, according to the most recent edition of the Global Terrorism Index.

The organization was also linked to another 20,000 deaths on various battlefields, the index found, but it did not indicate how many of the 26,000-plus deaths were specifically from IEDs.