UsageA Salvadoran colloquial expression meaning for a situation or problem to escalate and get worse rather than improve — la reunión iba mal y, cuando llegó el jefe, agarró fuego el cañal. It's a fixed regional idiom, not something to build with other tenses or subjects the way an ordinary verb works.
Examples- Todo iba bien hasta que agarró fuego el cañal. — Everything was fine until things went south.
- Si sigues discutiendo, va a agarrar fuego el cañal. — If you keep arguing, it's going to blow up.
- En cuanto se enteraron, agarró fuego el cañal. — As soon as they found out, everything fell apart.
Common mistakeTrying to use this outside El Salvador and expecting it to be understood — it's a narrowly regional fixed expression, not a general Spanish verb phrase; complicarse las cosas is the widely understood equivalent.