French authorities have stepped up security across Paris following a foiled bomb attack targeting offices of Bank of America, prompting several U.S. banks in Europe to allow staff to work remotely as a precaution.

Citing an elevated terrorist threat, Paris police said security has been reinforced around religious and cultural landmarks, diplomatic missions, and key economic sites across the العاصمة and wider metropolitan area.

French anti-terrorism prosecutors confirmed that four suspects—three teenagers and one adult—have been placed under formal investigation over their alleged involvement in last week’s attempted attack. The adult suspect is accused of recruiting the teenagers and paying them between €500 and €1,000 to plant and film the explosive device. All four suspects, currently in pre-trial detention, deny terrorist intent.

Authorities revealed that the improvised explosive device consisted of a five-litre petrol can attached to a large pyrotechnic charge, describing it as the most powerful device of its kind identified in France to date.

Police suspect the plot may be linked to a pro-Iranian group known as HAYI, which had previously released a video referencing Bank of America’s Paris headquarters. However, prosecutors say this connection has not yet been confirmed.

In response to the threat, major financial institutions including Goldman Sachs and Citigroup allowed employees in Paris and Frankfurt to work remotely on Thursday. Citigroup described the move as a precautionary measure.

French President Emmanuel Macron praised security forces for successfully preventing the attack and emphasized continued vigilance. Speaking during a visit to South Korea, he reassured the public that authorities remain alert as similar threats have emerged in other European countries.

Officials warn that the ongoing conflict involving Iran, which began with U.S. and Israeli strikes in late February, could increase the risk of retaliatory or inspired attacks in France. The country remains sensitive to such threats following the devastating Islamist militant attacks in 2015 that killed 147 people across separate incidents, leading to stricter national security measures.